Aerospace series. Paints and varnishes. Two-components room temperature curing polyurethane finish. High flexibility and chemical agent resistance for military application

2021 ◽  
2021 ◽  
Vol 5 (4) ◽  
pp. 110
Author(s):  
Flaminio Sales ◽  
Andrews Souza ◽  
Ronaldo Ariati ◽  
Verônica Noronha ◽  
Elder Giovanetti ◽  
...  

Polydimethylsiloxane (PDMS) is a polymer that has attracted the attention of researchers due to its unique properties such as transparency, biocompatibility, high flexibility, and physical and chemical stability. In addition, PDMS modification and combination with other materials can expand its range of applications. For instance, the ability to perform superhydrophobic coating allows for the manufacture of lenses. However, many of these processes are complex and expensive. One of the most promising modifications, which consists of the development of an interchangeable coating, capable of changing its optical characteristics according to some stimuli, has been underexplored. Thus, we report an experimental study of the mechanical and optical properties and wettability of pure PDMS and of two PDMS composites with the addition of 1% paraffin or beeswax using a gravity casting process. The composites’ tensile strength and hardness were lower when compared with pure PDMS. However, the contact angle was increased, reaching the highest values when using the paraffin additive. Additionally, these composites have shown interesting results for the spectrophotometry tests, i.e., the material changed its optical characteristics when heated, going from opaque at room temperature to transparent, with transmittance around 75%, at 70 °C. As a result, these materials have great potential for use in smart devices, such as sensors, due to its ability to change its transparency at high temperatures.


1958 ◽  
Vol 4 (5) ◽  
pp. 593-602 ◽  
Author(s):  
Ned Feder ◽  
Richard L. Sidman

Freeze-substitution is based on rapid freezing of tissues followed by solution ("substitution") of ice at temperatures well below O°C. A 1 to 3 mm. specimen was thrown into 3:1 propane-isopentane cooled by liquid nitrogen to -175°C. (with precautions). The frozen tissue was placed in substituting fluid at -70°C. for 1 week to dissolve ice slowly without distorting tissue structure. Excess substituting agent was washed out, and the specimen was embedded, sectioned, and stained conventionally. For best morphological and histochemical preservation, substituting fluids should in general contain both chemical fixing agent and solvent for ice, e.g., 1 per cent solutions of osmium tetroxide in acetone, mercuric chloride in ethanol, and picric acid in ethanol. Preservation of structure was poorer after substitution in solvent alone. Evidence was obtained that the chemical agent fixes tissue at low temperatures. The chemical mechanisms of fixation are probably similar to those operating at room temperature: new chemical cross-linkages, which contain the fixing agent, join tissue constituents together. This process is distinguished from denaturation by pure solvents. Freeze-substitution has many advantages, particularly the preservation of structure to the limit of resolution with the light microscope, and the accurate localization of many soluble and labile substances.


2014 ◽  
Vol 70 (a1) ◽  
pp. C788-C788
Author(s):  
Jean-Luc Ferrer ◽  
Xavier Vernede ◽  
Yoann Sallaz-Damaz ◽  
Christophe Berzin ◽  
Michel Pirocchi ◽  
...  

Development of 6-axis robotic arm based systems for protein crystallography automation is now expending rapidly. From the seminal work accomplished on beamline FIP-BM30A (ESRF) in 2000' to the present developments, robot based systems significantly changed the crystallography experiment strategy. They open possibilities for new strategies, give a high flexibility to the experimental setup, and make automation and remote control much easier. The robotized platform on which are based our present developments, named G-Rob, plays as a fully integrated, multi-purpose automated and remotely controlled diffractometer for beamlines and laboratories. G-Rob integrates several functions: classical sample changer; goniometer for frozen samples or capillaries [1], including frozen sample transfer from a storage Dewar; crystallization trays handling for in situ screening and data collection on crystallization plates and microchips [2]; powder diffraction; beam monitoring; on line crystal fluorescence/absorption; crystal harvesting; Etc. Thanks to its tool changer, the robot arm can go automatically from one application to another. G-Rob can be easily upgraded with new functions. Several G-Rob systems, both at synchrotrons (ESRF, LNLS, BNL) or as laboratory in-house systems (EPFL, CBS) are now available for the crystallography community. Among the last results obtained with G-Rob are: (i) Automated structure resolution at room temperature, for the analysis of protein dynamic; (ii) Automated structural screening for the fragment based drug design strategy. New functions are also under development, such as the remote controlled robotized crystal harvesting [3]. Such manipulations of individual crystals with the robot closes the gap for fully remote, and in the future fully automated, operation of crystallography pipeline.


2009 ◽  
Vol 113 (4) ◽  
pp. 1325-1328 ◽  
Author(s):  
Michael J. Coutts ◽  
Michael B. Cortie ◽  
Michael J. Ford ◽  
Andrew M. McDonagh

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1051
Author(s):  
Jiahao Gong ◽  
Qifu Wang ◽  
Bingxin Liu ◽  
Huimin Zhang ◽  
Lin Gui

A room temperature liquid metal-based microvalve has been proposed in this work. The microvalve has the advantages of easy fabrication, high flexibility, and a low leak rate. By designing a posts array in the channel, the liquid metal can be controlled to form a deformable valve boss and block the flow path. Besides, through adjustment of the pressure applied to the liquid metal, the microvalve can perform reliable switching commands. To eliminate the problem that liquid metal is easily oxidized, which causes the microvalve to have poor repeatability, a method of electrochemical cathodic protection has been proposed, which significantly increases the number of open/close switch cycles up to 145. In addition, this microvalve overcomes the shortcomings of the traditional microvalve that requires an alignment process to assemble all the parts. When the valve is closed, no leak rate is detected at ≤320 mbar, and the leak rate is ≤0.043 μL/min at 330 mbar, which indicates it has good tightness. As an application, we also fabricate a chip that can control bubble flow based on this microvalve. Therefore, this microvalve has great prospects in the field of microfluidics.


Author(s):  
Gen Hayase ◽  
Yasutaka Ohya

<p>Low bulk density porous monoliths were prepared by using two types of silicon alkoxide methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS) as precursors and controlling phase separation under appropriate conditions. By changing the ratio of the aqueous solution to the precursors in the starting composition, it was possible to control the microstructure of the resulting porous monoliths or to prepare microparticles. Those marshmallow-like monoliths with a skeleton diameter of a few micrometers and pore diameter of several tens micrometers has high flexibility against compression and bending, and shows low thermal conductivity of ~30 mW m<sup>−1</sup> K<sup>−1</sup> at room temperature. We show that those materials can be used as a simple cryopreserved embryo container like small dry shippers by packing gels and adsorbing liquid nitrogen in a vacuum-insulated water bottle.</p>


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